1. Field of the Invention
This invention relates to the field of photography and, more particularly, to a device which may be incorporated with a focusing control system of a photographic apparatus for indicating a distance at which an objective lens of the apparatus is focused.
2. Description of the Prior Art
Conventional low cost photographic cameras are designed to provide a reliable and consistent performance within the range of a photographic environment most often encountered by an amateur photographer. To derive an acceptable high success rate for a "snapshot photograph" for which the cameras are intended, the design of such cameras is tailored not only to meet rigid cost limitations but also to limit the number of adjustments to any exposure mechanism required for any one photograph.
Generally, distance determining devices, e.g., rangefinders, are not provided with conventional inexpensive cameras. Fabrication costs preclude an incorporation of such semi-automatic ranging devices into the cameras. In an attempt to expand the camera's usefulness, recently developed low cost cameras are structured to include mounting devices and electronic circuits for providing flash illumination. In this mode of operation, the scope of range of performance of the cameras is somewhat limited in comparison to their use under ambient conditions. The amateur photographer must remain aware of camera-to-subject distance when the camera is operated in the flash mode. In the flash mode, a light generating capacity of a flashbulb being utilized in generally determined in accordance with the "inverse square law" which assumes that light emanating from the bulb dissipates in proportion to the square of a distance from the source. Furthermore, the amateur photographer is often not mindful of the difference in operational scope of the camera when using artificial illumination as opposed to ambient lighting. Consequently, without the assistance of a device which aids the operator in bringing the camera into coincidence with an optimum distance for photographs taken in the flash mode, a relatively high percentage of exposures made by the amateur photographer are aborted. Therefore, an inexpensive means is required beyond mere admonitions in film package instructions for reminding the photographer to determine the optimum camera-to-subject distance and make the exposures within that range only.
U.S. Pat. No. 3,315,579, issued on Apr. 25, 1967 to E. H. Land for "Dual Mode Control Means" discloses and defines control apparatus whereby an exposure value setting for a shutter mechanism operating under steady state light conditions is established by the use of a built-in photometer. With this arrangement, the diaphragms of the photometer apparatus and the exposure aperture may be adjusted until the area of the exposure aperture is correct for the level of scene brightness. However, the above procedure is applicable only to a scene under steady state lighting conditions or at a level exceeding some minimum value of scene brightness at which the photometer is operative. When the scene brightness is less than the minimum value, proper exposure can be achieved by using a flash bulb. With flash illumination, the area of the exposure aperture is achieved by adjusting the relative position of a pair of movable elements to define a proper aperture as a function of the distance of the subject to the camera. A distance scale is provided therefor by imprinting a pointer and indicia forming a scale graduated respectively in distance units upon a flange of one of the pair of movable elements such that the relative position of the elements defines the area of the exposure aperture for proper exposure of the photographic subject in the flash mode of operation over a range of camera-to-subject distances. The pointer is aligned with one of the distance units at a window provided therefor in a shutter housing of the camera whereby the operator is apprised, when the movable elements have been adjusted, to provide the proper aperture setting for the predetermined camera-to-subject distance, of the distance for which the exposure aperture is set thereby substantially improving the operation of a fixed speed, fixed focus camera in the flash mode.
Camera-to-subject distance determination are also critical where popular priced cameras are designed for use with relatively slower speed film, for instance, color film as compared with black and white film. For such applications, simple, relatively inexpensive, variable focusing lens arrangement which is manually adjustable at distance settings corresponding to the camera operator's estimation of a camera to subject distance and an inexpensive but accurate distance indicator may be combined to aid the operator in accurately focusing the camera over an extended range of camera-to-subject distance.
In the past, operators of conventional low cost cameras having a conventional viewfinder and variable focusing lens have first estimated the camera-to-subject distance and then focused the lens for that distance by aligning a scale graduated in distance units circumferentially arranged about the lens housing with an index mark included upon a face of the camera. In order to focus the lens the operator may find it necessary to lower the camera from the viewing position and look away from the photographic scene during the focusing of the lens. While this may not be an inconvenience for an experienced organized operator, it may disrupt the concentration of the inexperienced amateur who may subsequently discover upon returning the camera to the viewing position that too little or too much information, as it relates to the photographic scene, is presented within the viewfinder and must compensate therefor by moving either the camera or the subject to a new position whereat all of the desired image of the photographic scene is contained within the viewfinder. Much too often, the amateur operator fails to refocus the lens for the new position before releasing the shutter whereby the resulting photographic prints are substantially out of focus.
Frequently, an operator may wish to photograph different views of the same photographic scene. While quickly moving about to each new location, the operator may forget to refocus the lens for each new camera-to-subject distance and continue to operate the camera at a focal setting which is inappropriate for a substantial number of the scenes whereby the resulting photographic prints shall be out of focus. Each time the operator may remember to focus the lens for each new camera-to-subject distance, it shall be necessary for the operator of a camera of this type to lower the camera from the viewing position and turn it to a position whereat the operator may view the alignment of the distance scale with the index mark on the face of the camera and then return the camera to the viewing position before releasing the camera's shutter. As a result, the concentration of the operator may be disrupted and the operator shall be required to recompose the photographic scene within the viewfinder which may be particularly frustrating to the operator and often to the photographic subject.
Therefore, in U.S. Pat. No. 3,583,300, issued on June 8, 1971, to Bruce K. Johnson, for "Photographic Camera with Viewfinder" a photographic camera is disclosed including an adjustable distance scale upon a bezel encompassing a lens of the camera including a viewfinder mounted upon the camera such that an image of the distance scale is presented in or beside a field of view of the viewfinder. This arrangement permits the operator to make a preliminary visual estimate of the camera-to-subject distance and then raise the camera to a viewing position whereat the operator may focus the lens by moving the distance scale to an appropriate index mark thereon while viewing an image of the photographic scene. The arrangement further serves to remind the operator of the distance at which the lens is focused and should the setting be obviously in error, it will be obvious to the operator and a proper correction can be made before the camera's shutter is released.
The viewfinder is mounted upon an upper surface of the camera and is displaced a substantial distance from a variable focusing lens. The lens is incorporated within a lens bezel rotatably mounted to extend externally beyond a forward wall of the camera's housing as disclosed in U.S. Pat. No. 3,893,221 issued on Dec. 26, 1973 to Walter G. Lehman, for "Lens Assembly Mounting Method and Apparatus." The lens bezel includes, upon an outer peripheral surface, a distance scale for indicating to the operator a distance at which the lens is focused. A periscope-like system is mounted forward of the face of the camera and extends above the lens bezel within a housing provided therefor for directing an image of the distance scale into the viewfinder whereby the operator may observe the distance scale's image simultaneously with an image of the photographic scene during the focusing of the lens for a preselected, visually estimated distance.
However, the periscope-like system includes a plurality of reflectors having mirror surfaces which must be precisely positioned within the housing in order to direct the image of the scale in the direction of a specially adapted refracting portion provided therefor upon a lens of the viewfinder which substantially adds to the manufacturing cost of the camera. In addition thereto, the objective lens of the camera is threadably secured within the lens bezel and is adapted to remain externally beyond the forward face of the camera for external movement towards and away from the forward face during the focusing of the lens between the distant and nearmost foci. The lens bezel is rotated for rectilinear movement of the lens along its optical axis during the focusing of the lens between the distant and nearmost foci whereby the distance scale moves beneath the periscope-like system and remains within the field of view of the operator within the viewfinder during the focusing of the lens. While the periscope-like system may be adapted for use with most conventional cameras, it is more suitably adapted for use with cameras of the non-folding type having an externally mounted lens wherein the externally mounted optical systems do not conflict with an design. Incorporating such an arrangement with a compact folding camera would substantially add to the overall length and thickness of the camera when the camera is collapsed, thereby defeating the purpose of the design.
By incorporating a compound lens system having at least one movable element adapted to move axially and rectilinearly between a distant and nearmost foci, within a shutter housing of the camera, a variable focusing, compact, folding camera may be developed having an overall thickness no greater than the thickness of the shutter housing when the camera is collapsed into the folded position.
The lens system developed therefor enables the movable lens to be rectilinearly displaced along the optical axis within the shutter housing whereby the hyperfocal positioning of the lens assembly is extended to include sharp focusing for a variety of camera-to-subject distances. U.S. Pat. No. 3,619,036 issued on Nov. 9, 1971, to James G. Baker, for "Compact Four Element Photographic Objective Lens" is typical of such systems and discloses a four element objective lens which employs front-element focusing. The front element moves rectilineraly within the shutter housing of the camera and even in its forwardmost position never extends beyond a forward wall of the shutter housing. Therefore, the periscope-like system in the aforementioned U.S. Pat. No. 3,583,300 and could not be adapted for use with such a lens assembly to provide the desired performance characteristics necessary for viewing the image of the scale within the viewfinder of such a camera.
In recent copending application, U.S. Pat. No. 3,971,052 issued on July 20, 1976, in the name of William T. Plummer, for "Compact Galilean Viewfinder," a photographic camera clearly resembling a compact, folding Polaroid SX-70 Land Camera, as made and sold by Polaroid Corporation, Cambridge, Massachusetts, was disclosed which enabled the manufacturer to substantially reduce the cost of the original version by simply substituting a viewing system for the through-the-lens viewing system of the original SX-70 camera and adding an external focusing scale upon a ring surrounding the lens. The focusing scale, however, is not visible to the operator within, beneath or beside the field of view of the viewfinder. In addition thereto, the characters comprising the scale are arranged about the peripheral edges of the ring which is relatively small for developing a distance scale and thereby severely restricts the size of the characters. Again, the operator is required to remove the camera from the viewing position to a position whereat the operator may adjust the scale and make the appropriate setting before the camera is raised to review the photographic scene. The previously cited Polaroid SX-70 Land camera may be modified for use with the viewing system as disclosed in the aforementioned U.S. Pat. No. 3,971,052. The camera includes a compound lens system mounted within a shutter housing having a movable element and manually rotatable focusing knob coupled thereto for focusing the lens assembly by advancing or retracting its movable element within the boundaries of the shutter housing. At least one element of the lens assembly is mounted within a lens bezel for rectilinear movement between distant and nearmost foci within a focusing barrel included within the forward wall of the shutter housing. The lens bezel includes indicia forming a distance scale arranged close to the peripheral edges of the lens assembly. The lens assembly is brought into focus for each visually estimated camera-to-subject distance by rotation of the focus wheel whereby the lens assembly is moved to align indicia representative of that distance with an index mark extending longitudinally upon an inner surface of the focus barrel. The viewing system is mounted upon the camera such that an uppermost surface of the shutter housing of the camera is visible within the field of view of the operator when the operator is viewing the photographic scene through the viewfinder. However, the focusing scale provided therewith, as with most internally housed lens assemblies, is not readily accessible to the operator from the rear of the camera. The concentration of the operator upon the scene may be disrupted when the operator is required to lower the camera from the viewing position and turn the camera to a position whereat the forward wall is facing the operator whereby the operator may view the movement of an appropriate character on the distance scale in alignment with the index mark.
In accordance with the present invention, it will be seen that a substantially simplified, inexpensive version of a focusing scale is provided which can be adaptably coupled to a focusing mechanism of such a camera and is positioned upon the camera in a convenient location whereby the operator is visibly reminded of the distance at which the lens is focused. The invention may be incorporated with a camera having a lens adjustably mounted for movement between a distant and nearmost foci within a shutter housing of the camera or mounted externally, i.e. beyond a forward face of the housing of the camera.